LCL filter for smoothing grid current of PV inverter is better than simple L-filter. However,there is possible instability of the LCL filter system caused by the zero impedance at the resonance frequency. The stability degradation phenomenon of the inverter with inverter side current control with increasing of digital delay was revealed. Then inverter side current control scheme based on capacitive voltage feed-forward was proposed. The inverter side current control scheme based on capacitive voltage feed-forward realized the reduction of system order by the feed-forward of capacitance voltage and effectively improved the stability of system. Then the influences of digital delay and feed-forward coefficient on the stable effect of capacitance voltage feed-forward were analyzed in detail. The effectiveness of the control strategy is verified by experimental results in a 630 kW three-phase grid-tied inverter.%并网逆变系统中,LCL滤波器相比单电感滤波器具有更优的滤波性能,然而引入了谐振点,降低了系统稳定性.揭示了存在数字延时LCL型并网逆变器逆变侧电流单环控制的稳定性恶化现象,提出了一种基于电容电压前馈的逆变侧电流控制方案,该方案通过电容电压前馈使系统降阶,从而有效地改善了系统的稳定性,同时分析了延时和前馈系数对电容电压前馈效果的影响.所提控制方案的有效性在自行研制的630 kW三相逆变器上得到了实验验证.
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